There is a shocking difference between President Obama’s public and personal position on the issue of marijuana. The contradiction is troubling, to say the least.

In a headline-making interview published by The New Yorker magazine, Mr. Obama was casually dismissive about the dangers of getting high on the drug.

“As has been well documented,” the president admitted, “I smoked pot as a kid, and I view it as a bad habit and a vice, not very different from the cigarettes that I smoked as a young person up through a big chunk of my adult life. I don’t think it is more dangerous than alcohol.”

Mr. Obama did say that smoking marijuana is “not something that I encourage, and I’ve told my daughters I think it’s a bad idea, a waste of time and not very healthy.”

But the tone of his public remarks characterizes the use of pot — which is legal only in the states of Colorado and Washington — much more as a vice than a crime.

In fact, what Mr. Obama told The New Yorker about the use of marijuana was far less emphatic than his own administration’s position as presented by the White House Office of National Drug Control Policy.

It says the Obama administration “steadfastly opposes legalization of marijuana and other drugs” because that would “pose significant health and safety risks to all Americans, particularly young people.”

At its website (whitehouse.gov/ondcp), the White House Office of National Drug Control Policy makes a strong case against smoking pot. It warns: “Confusing messages being presented by popular culture, media, proponents of ‘medical’ marijuana, and political campaigns to legalize all marijuana use perpetuate the false notion that marijuana is harmless.”

The White House office states that marijuana has “a high potential for abuse” because of the chemical ingredient THC, which influences pleasure. It also affects sensory and time perception, thinking and coordinated movement.

Citing the impact of marijuana in 2011, the White House office reports: “Approximately 4.2 million people met the diagnostic criteria for abuse of or dependence on this drug. This is more than pain relievers, cocaine, tranquilizers, hallucinogens, and heroin combined.”

Research is cited that suggests about 9 percent of those who regularly use marijuana eventually become dependent on the drug.

The White House Office of National Drug Control Policy points to findings that show chronic pot smoking can increase the risk of schizophrenia in vulnerable people and high doses can lead to acute psychotic reactions.

In 2011, more than 870,000 Americans reported that they received medical treatment for the side effects caused by marijuana, more than did so for any other illicit drug.

All of which suggests that caution is the best approach when it comes to the subject of marijuana.

This is something the president ought to consider when discussing the matter.